Various display cartons, advertising devices and folding structures typically fabricated of cardboard are heretofore known. For example, see FLYNN, U.S. Pat. No. 1,491,091, SCHWARTZ, U.S. Pat. No. 2,788,596 and THOMAS, U.S. Pat. No. 3,508,734. Such foldable devices, however, have numerous disadvantages when considering the fabrication of permanent shelving.
First, they are typically fabricated of a material not having the property of angular memory when formed. That is to say, in their fabrication cardboard or the like is typically freely hinged about the fold axis. Once hinged and bent, it no longer preserves any angular rigidity. Structural soundness is typically lost along the plane of the hinge.
Moreover, such units are typically comprises of separately cut pieces, folded separately and thereafter joined one to another. Multi-piece fabrication requires an undue amount of time and often results in significant material wastage.
Also disclosed in the prior art is a method of making a one-piece display device formed from a single sheet of plastic. The sheet is cut or slit and bent at various points after heating. While this method overcomes many of the shortcomings noted above, the structures thus fabricated have a number of disadvantages which are foreign to the present invention. The method does not yield a conventional, simple shelf case having two sidewalls, a rear wall, and at least one horizontal shelf. Instead, it yields rather complex, multi-level, multi-angled, cantilevered display devices. Complex cuts and folds must be made. The devices are not suitable for wall mounting. The shelves have little bending resistancy when loaded. All of the display devices fabricated utilizing this method are unsuitable for use as book cases.
In contrast, the present invention yields a conventional, simple shelf structure. A minimal number of cuts and folds is required. The cuts are made with rounded corners to reduce the liklihood of cracking that might occur if right-angle cuts defining sharp corners were made. Carefully located apertures linking segments of the cut defining a single shelf, allow the shelf to be bent to form an L-beam configuration and allow the tabs of the shelf ends to be inserted into slots in the sidewalls without buckling of material at the corners. The tab-to-slot joints and the L-beam configuration result in a sturdy shelf which resists bending even under considerable loading conditions. The shelf case of the present invention is readily adaptable to wall mounting which further adds strength by providing rear wall cross bracing.